it fixes an issue with SDXL if you have called `enable_sequential_cpu_offload()` on your pipeline. you'll need to pass eg `device='cuda'` to compel's `__init__`.
i also cleaned up the SDXL demo notebook and extended it to demonstrate using positive+negative and long prompt support with the `__call__` interface (i.e. `compel([positive_prompt, negative_prompt])`).